<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <div id="app">
        <button @click="flag=!flag">click</button>
        <div style="width: 100px;height: 100px;background: gray" v-show="flag">

        </div>
    </div>
</body>
<script src="./js/vue.js"></script>
<script>
    Vue.config.productionTip = false
    new Vue({
        el:"#app",
        data:{
            flag:true
        }
    })
</script>
</html>